Abstract
In northern Kyushu, in Japan, the azuki bean(Vigna angularis(Willd.)Ohwi & Ohashi)is usually sown in spring. The seed quality is inferior to that harvested in Hokkaido because the seed fills under the conditions of high temperature and high humidity in summer. In this report, the effect of summer sowing on the seed quality for 8 early maturing cultivars of azuki bean were investigated for two years. The increase in seed size and the decrease in seed coat content and hard seed frequency were observed in all cultivars by summer sowing in 1993. According to the results of 1995, the seed size and seed coat content of plants sown after July 21, and the seed coat color of plants sown after July 31, were superior to those of other sowings. These characteristics could stand comparison with those of seeds harvested in Hokkaido. However, the hard seed frequency was a little higher than in Hokkaido in 1995. In the case of sowings on July 31 and August 12, not only was the seed yield high, but also the harvest was easy because pods matured uniformly and almost all the leaves defoliated before the harvest time. Therefore it is recommended that the azuki bean be sown from the end of July to the middle of August in northern Kyushu, Japan.
